Screen filter

In standardized testing (EN444, EN1435) with x-ray films one must work above 100 keV with front and back screens (generally of lead) for amplification and filtering. Lead screens filter... 

Barrier Phenomenon. In red cell filtration, the blood first comes into contact with a screen filter. This screen filter, generally a 7—10-) m filter, does not allow micro aggregate debris through. As the blood product passes through the deeper layer of the filter, the barrier phenomenon continues as the fiber density increases. As the path becomes more and more tortuous the cells are more likely to be trapped in the filter. 

Fig. 26. Screen filters contain pores of a uniform size and retain all particulates greater than the pore diameter at the surface of the membrane. Depth filters contain a distribution of pore sizes. Particulates entering the membrane are trapped at constrictions within the membrane. Both types of filters are rated 10...

Fig. 27. Scanning electron micrograph (a) and cross-sectional comparison (b) of screen and depth filters both having a nominal particulate cut-off of 0.4 flm. The screen filter (a Nuclepore radiation track membrane) captures particulates at the surface. The phase-inversion ceUulosic membrane traps the...

Wolber G, Langer T LigandScout 3-D pharmacophores derived from protein-bound ligands and their use as virtual screening filters. / Chem Inf Model 2005 45 160-9. 

Remedying the problem of clot formation and its detrimental effect on sample transfer has also been addressed in a recent publication from the Johnson Johnson Pharmaceutical Research and Development Laboratories161 where workers designed a novel 96-well screen filter plate consisting of 96 stainless steel wire-mesh screen tubes (Figure 1.42). 

The advantages of this screen filter, as cited by the authors, consist of its reusability, its standard 96-well format size, and its ability to be used whenever sample transfer or pipetting is needed. After usage, the screen filter can be easily cleaned by rinsing with water and methanol and additionally, by ultrasonication in water or methanol or other appropriate solution. The filter can be inserted into a plasma storage plate before sample transfer by the Tomtec Quadra used by the authors for automation. 

Screen centrifuge conical, 5 546-548 continuous cylindrical, 5 545-546 Screen decks, 22 279-281 deck area of, 22 281-282 Screened quicklime, 15 65 uses for, 15 61-62 Screen filters, 15 827, 828 Screening... 

The maximum solvent operating temperature is calculated as the boiling temperature minus a 15°C safety margin, to prevent product crystallization and blockage when screening (filtering) between the dissolver and crystallizer. Section 1.1.4. 

An aluminum enclosure housed the working components of the cotton-dust analyzer. The upper section of the enclosure, which was hinged to the lower section, contained the HEPA filter, the spray bar assembly, and the top, hold-down screen for the lint batt. The botton section housed the sizing screen, filter support, fan, and the electrical and pneumatic controls. The entire enclosure was 60 cm wide, 46 cm deep, and 72 cm tall. 

These applications of virtual screening filters and methods with increased complexity are dependent on the stage at which they are used in the virtual screening work flow. 

Zuegge, J., Fechner, U., Roche, O., Parrott, N., Fngkvist, O. A fast virtual screening filter for cytochrome... 

Schneider et al. (245) used 333 one and two-dimensional descriptors to create a virtual screening filter for CYP 3A4 inhibition. After the application of a space-... 

Filters can be divided into two types membrane (screen) filters and depth filters. Membrane filters, such as silver membrane filters, physically screen and retain particles on their surfaces. These filters have uniform pore sizes and are rated for absolute retention all particles larger than the pore size are retained. Depth filters, such as glass-fiber filters, consist of a matrix of fibers that form a tortuous maze of flow channels. The particulate fraction becomes entrapped by this matrix. These filters do not have a uniform pore size, and it is not possible to rate them for absolute retention. They are rated according to nominal pore size, which is determined by the particle size that is retained by the filter to a predetermined percentage. This percentage is usually given as 98 retention however, it can be as low as 90. ... 

The poly(vinylidene chloride-cu-vinylchloride) may be injection molded and extruded. Extruded pipe and molded fittings which were produced in large quantity in the 1940s have been replaced to some extent by less expensive thermoplastics. A llal extruded filament is used for scouring pads and continuous extruded circular filament is used for the production of insect screening, filter clothes, fishing nets and automotive seat covers. 

Devolatilization removal of vaporizable material by the action of heat. Dewatering removal of water from coal by mechanical equipment such as a vibrating screen, filter, or centrifuge. 

Filtration. To separate the dissolved from the particulate fraction filtration or centrifugation will be necessary. This causes a severe risk of contamination it is therefore often not carried out with open ocean samples, where the concentrations of suspended material are low. The presence of phytoplankton or a variable concentration of suspended matter affects the total concentration and a comparison of samples can thus become difficult. In speciation Studies the presence of particles may influence the results even more (complexation, adsorption), therefore filtration over acid washed membrane or screen filters in an appropriate filtration apparatus is recommended for all natural samples (Bewers et al., 1985). High pressure during filtration should be avoided ruptured (plankton-) cells will contribute organic matter, nutrients and trace metals to the solution. A pressure < 25 kPa is recommended (Florence and Batley, 1980). 

Microporous ultrafiltration and microfiltration membranes used to filter particulates from liquids fall into the two general categories illustrated in Figure 2.31. The first category (a) is the surface or screen filter such membranes contain surface pores smaller than the particles to be removed. Particles in the permeating... 

The mechanism of particle filtration by screen filters has been the subject of many studies because it is relatively easily described mathematically Bungay has published a review of this work [49], Ferry [50] was the first to model membrane retention by a screen filter in his model pores were assumed to be equal circular capillaries with a large radius, r, compared to the solvent molecule radius. Therefore, the total area of the pore is available for transport of solvent. A solute molecule whose radius, a, is an appreciable fraction of the pore radius cannot approach nearer than one molecular radius of the pore overall. The model is illustrated in Figure 2.32. 

The two principal types of microfiltration membrane filter in use—depth filters and screen filters—are illustrated in Figure 7.3. Screen filters have small pores in their top surface that collect particles larger than the pore diameter on the surface of the membrane. Depth filters have relatively large pores on the top... 

Depth membrane filters are usually preferred for in-line filtration. As particles are trapped within the membrane, the permeability falls, and the pressure required to maintain a useful filtrate flow increases until, at some point, the membrane must be replaced. The useful life of the membrane is proportional to the particle loading of the feed solution. A typical application of in-line depth microfiltration membranes is final polishing of ultrapure water just prior to use. Screen membrane filters are preferred for the cross-flow microfiltration systems shown in Figure 7.1(b). Because screen filters collect the retained particles on the surface of the membrane, the recirculating fluid helps to keep the filter clean. 

Figure 7.3 Surface scanning electron micrograph and schematic comparison of nominal 0.45-p.m screen and depth filters. The screen filter pores are uniform and small and capture the retained particles on the membrane surface. The depth filter pores are almost 5-10 times larger than the screen filter equivalent. A few large particles are captured on the surface of the membrane, but most are captured by adsorption in the membrane interior...

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